With regard to your query, Plan 299 does not include internet subscription with Globe that's why you still need to get a 5mb plan so you can go online.

Nokia Lumia 625 has Wi Fi feature, You need to turn it on from your settings menu. Turning on Wi Fi on your device does not necessarily mean that you will have internet connection, You will need first to connect to a Wi Fi hotspot let's say for example Starbucks before you can browse the net.